The present invention relates to bile acid or bile salt fatty acid conjugates (hereinafter called xe2x80x9cBAFACxe2x80x9d), to their use in dissolving cholesterol gallstones in bile, preventing their occurrence or recurrence, to their use in reducing or preventing arteriosclerosis and to methods for the treatment of said diseases.
It should be noticed that the terms bile acids and bile salts are similar and are used interchangeably.
Gallstones are found in about 15% of people in most industrialized countries. Most gallstones are cholesterol gallstones, i.e. cholesterol being their main component. Thus, cholesterol gallstones represent a major health problem. Bile is often supersaturated with cholesterol which tends to crystallize. The prevention of cholesterol crystallization in bile will prevent the formation of cholesterol gallstones or their recurrence after procedures such as lithotripsy, dissolution, or stone extraction. The residence time of newly secreted bile in the gallbladder is shortxe2x80x94less than 12-24 hours. The prevention of cholesterol crystallization in bile during such a period could prevent gallstone formation.
It has been proven that cholesterol gallstones can be dissolved medically and their recurrence prevented using certain bile salts such as chenodeoxycholic or ursodeoxycholic acid. Bile salt therapy is, however, of low efficacy, is very time consuming and has been largely abandoned. More effective therapies are thus required.
Recent work has demonstrated the major role played by phospholipids in cholesterol solubilization in bile. (T. Gilat et. al. Biochimica et Biophysica Acta 1286, (1996), 95-115; Y. Ringel et al. Biochimica et Biophysica Acta 1390, (1998), 293-300,); and J. Heptalogy, 28, (1998), 1008-1014.) Phospholipids are a major or sole component of cholesterol solubilizing lipid aggregates in bile. It has been demonstrated that the stepwise addition of phospholipids to bile will progressively prolong the nucleation time of the cholesterol in bile. (Z. Halpern et. al. Gut 34 (1993) 110-115).
Major differences between certain phospholipid molecular species in their cholesterol crystallization inhibiting potency in human or model biles have been demonstrated. Phospholipids differ from one another mainly in the fatty acids present in the stereo-specific number sn-1 and/or sn-2 positions and in their head groups. It has been demonstrated that major prolongations in the nucleation time and major reductions in the cholesterol crystal growth rate and in the total cholesterol crystal mass are achieved with changes in phospholipid molecular species without changing the absolute or relative amounts of phospholipids. Cholesterol crystallization was markedly delayed when the sn-2 fatty acid was saturated, when the head group was serine instead of choline, etc. (Y. Ringel et. al. above).
It has also been shown that various phospholipid components by themselves (without the whole phospholipid molecule), e.g. saturated fatty acids such as palmitic acid or stearic acid; or phosphatidyl glycerol have strong cholesterol crystallization inhibiting activity.
Thus, enriching human bile with phospholipids in general, or specific phospholipids or their components, such as fatty acids would markedly retard cholesterol crystallization in bile and achieve the desired result.
The problem was how to enrich human bile in vivo with phospholipids or their components. While bile salts are fed to humans they are very efficiently absorbed, taken up by the liver and excreted into bile. This also applies to synthetic bile salt analogues. There are specific and very efficient transport mechanisms in the body for these purposes. Thus, when ursodeoxycholic acid (which is normally present in human bile in minute amounts) is fed regularly it is absorbed and secreted into bile and eventually constitutes 30-50% of biliary bile acids. However, as indicated above bile salt therapy for the dissolution of cholesterol gallstones is not satisfactory.
Phospholipids and their components are well absorbed and taken up by the liver. Phospholipid secretion into bile is, however, tightly regulated by the liver and only limited amounts and species of phospholipids are secreted into bile in association with the secretion of bile salts and cholesterol. There is at present no efficient method to modulate, quantitatively or qualitatively, human biliary phospholipid compositions to any considerable degree. When dietary phospholipids reach the liver they may be metabolized, secreted into the blood or stored in the liver. Only small amounts and predetermined species are secreted into bile with minimal possibilities for modulation.
It has therefore been desirable to find a satisfactory method for the transport of phospholipids or one of their components into bile which would improve the solubilization of biliary cholesterol and prevent the formation of cholesterol gallstones or dissolve existing gallstones.
From Israel Patent specification No. 95668 and corresponding U.S. Specifications there are known bile acid derivatives of general formula I:
Wxe2x80x94Xxe2x80x94G
in which G is a bile acid radical, W is an active compound moiety of a medicament and X is either a direct bond or a bonding member between said bile acid radical and the active compound. In said specifications a long list of substituents is given but it does not mention specifically W as standing for a fatty acid radical, neither for a saturated one nor for an unsaturated one, i.e. said specifications do not mention anything about BAFAC.
Moreover, among all the objects of said compounds their cannot be found even a hint that any of said compounds may be utilized to enhance the solubilization of biliary cholesterol, to prevent the formation of cholesterol gallstones, to dissolve existing cholesterol gallstones, to reduce or prevent arteriosclerosis.
It has now been found that bile acids or salts conjugated with fatty acids (saturated or unsaturated) via a connecting bond xe2x80x94NHxe2x80x94 (BAFAC) can serve as vehicles to transport the fatty acids into the bile using the very efficient entero-hepatic circulation of bile acids and salts.
An ester bond between the fatty acid(s) and the bile acid is unsuitable as it would be broken down by digestive juices and intestinal bacteria during absorption and enterohepatic circulation. Only a fraction of the intact BAFAC will remain in the bile.
It has also been shown that BAFAC are absorbed from the intestine, taken up by the liver and secreted into bile. Said BAFAC improved cholesterol solubilization in bile and markedly retarded its crystallization. Said BAFAC are therefore useful agents for the prevention of the formation or recurrence of cholesterol gallstones and for the dissolution of cholesterol gallstones.
The administration of BAFAC has also an inhibiting effect on cholesterol crystallization in the vascular tree. In the physiologic situation ingested bile acids or salts are absorbed in the intestine, transported via the portal vein to the liver and excreted via the bile into the intestine. They thus recirculate in the entero-hepatic circulation, with only small amounts reaching the systemic circulation (the vascular tree). The BAFAC behave more like lipids, which after intestinal absorption are transported via the lymph to the systemic circulation. The BAFAC were shown to be transported both via the lymph and via the portal vein. By both routes they are taken up by the liver and secreted into the bile. At each entero-hepatic circulation they are excreted into the intestine, are again partly reabsorbed via the lymph and recirculated into the vascular tree prior to liver uptake. As there are daily 10-12 cycles of entero-hepatic circulation the net effect will be recirculation of the BAFAC in the vascular tree.
Administration of BAFAC orally in divided doses in the course of the day will enhance this effect. The inhibiting effect of BAFAC on cholesterol crystallization and their effectiveness in dissolving existing cholesterol crystals has been proven. Thus, also their value in reducing and/or preventing cholesterol crystallization in the vascular tree, i.e. in arteriosclerosis.
The present invention thus consists in bile acid or bile salt fatty acid conjugates of general formula II:
Wxe2x80x94Xxe2x80x94G
in which G has the same meaning as in formula I, which, if desired, is conjugated in position 24 with a suitable amino acid, W stands for one or two fatty acid radicals having 18-22 carbon atoms and X stands for a NH bond between said bile acid or bile salt radical and the fatty acid radical(s).
As suitable bile acids they may be mentioned, e.g. cholic acid, chenodeoxycholic acid, ursodeoxycholic acid and deoxycholic acid. The bile acids utilized may be unconjugated or, as in bile, be conjugated with glycine, taurine or another suitable amino acid. These possibilities are within the definition of a bile acid and thus within the scope of the present invention. The conjugation with the fatty acid radical is mostly performed at position 3 of the nucleus depending on the bile acid being used. It is also possible to perform the conjugation with the fatty acid radical at different positions, e.g. 6, 7, 12 and 24. When the bile acid is conjugated with glycine or taurine the conjugation with the fatty acid radical cannot be performed in position 24. The conjugation between the fatty acid radical and the bile acid can be in the xcex1 or the xcex2 configuration.
Preferred fatty acids are saturated ones which have suitably 18-22 carbon atoms. Preferred saturated fatty acids are behenylic acid, arachidylic acid and stearic acid.
When W stands for two fatty acids they are suitably conjugated at positions 3 and 7.
The present invention also consists in a pharmaceutical composition enabling the dissolution of cholesterol gallstones in bile and preventing the formation thereof; and enabling the prevention and/or reduction of arteriosclerosis, comprising as active ingredient a bile acid fatty acid derivative of general formula II.
Said composition may have the form of a tablet, a capsule, a solution, an emulsion, etc.
Said composition may comprise additional compounds such as carriers, solvents, emulgators, enhancers of absorption, inhibitors of cholesterol synthesis or secretion into the bile, etc. Said composition should advantageously comprise 0.1-1.5 g of the active ingredient.
The composition is suitably ingested once daily preferably at bedtime. It may also be ingested in divided doses during the day.
The present invention also consists in the use of a bile acid fatty acid derivative of general formula II or of a pharmaceutical composition comprising same for the dissolution of cholesterol gallstones in bile and for the prevention of the formation thereof.
The present invention also consists in the use of a bile acid fatty acid derivative of general formula II or of a pharmaceutical composition comprising same for the prevention and/or reduction of arteriosclerosis.
The present invention also consists in a method for the dissolution of cholesterol gallstones in bile and for the prevention of the formation thereof by administering a bile acid fatty acid derivative of general formula II or a pharmaceutical composition comprising same.
The present invention also consists in a method for the prevention and/or reduction of arteriosclerosis by administering a bile acid fatty acid derivative of general formula II or a pharmaceutical composition comprising same.
The present invention will now be illustrated with reference to the accompanying Examples and drawings without being limited by them.